Lock for turbomachinery blades



Aug. 6, 1968 J. c. BURG-E ETAL 3,395,891

LOCK FOR TURBOMACHINERY BLADES Filed Sept. 2l. 1967 2 Sheets-Sheet l ug. 6, 1968 J. c. BURGE ETAL LOCK FOR TURBOMACHINERY BLADES 2 Sheets-Sheet Filed Sept. 2l, 1967 few; ai

United States Patent O 3,395,891 LOCK FOR TURBOMACHINERY BLADES Joseph C. Burge, Cincinnati, and Richard Beal, Loveland,

Ohio, assignors to General Electric Company, a corporation of New York Filed Sept. 21, 1967, Ser. No. 669,454 4 Claims. (Cl. 253-77) ABSTRACT OF THE DISCLOSURE This disclosure illustrates a fragmentary portion of a compressor rotor rim having tanged blades which are locked thereon by locking devices lying between the bottoms of the tangs and slots in the rim. The locking devices comprise a retainer having legs embracing the opposite sides of the rim and one leg engaging one end of the tang. A spacer maintains the blade in an elevated position and has a leg which engages the opposite end of the tang. The retainer and spacer are held together by a bolt. Upon removal of the bolt and the spacer, the blade may be dropped radially inwardly to clear a midspan shroud between adjacent blades and thus enable the blade to be removed from the slot. The bolt is threaded into a captured nut on the inner member so that assembly and disassembly can be had from one side of the rotor.

The invention described and claimed in the United States patent `application herein resulted from work done under United States Government contract FA-SS-66-6. The United States Government has an irrevocable, nonexclusive license under said application to practice and have practiced the invention claimed herein, including the unlimited right to sublicense others to practice and have practiced the claimed invention for any purpose whatsoever.

The present invention relates to improvements in turbomachinery rotors and more specifically to an improved mechanism for locking blades in place on such rotors.

In the manufacture of bladed turbomachinery rotors, it is common practice to mount the blades on the rotors through the use of tangs formed at the base of the blades which are received by corresponding slots formed across the peripheral face of the rotor. It has been a commonly accepted practice also, particularly in gas turbine engines for the propulsion of aircraft, to lock the blades in the rotor slots by the use of metal strips which are slipped through the rotor slots and their ends bent so that they overlie both the tang and adjacent portions of the side of the rotor. This is a simple arrangement which enables individual lblades to be replaced if desired.

It has the disadvantage, however, that any relative movement between the blade and the rotor, in an axial sense, will be taken by a portion of the retainer which has been bent after assembly. While such a retainer can be designed to function satisfactorily, if an attempt is made to reuse it or if it is not designed exactly as specified or used exactly as specified, reliability problems can arise. A further problem is that the bent metal tab retainers are not particularly suitable for locking blades having shrouds either intermediate their length or their outer ends. Shrouded blades require that the blade be shifted radially inwardly before it can be removed from the slot. Yet another drawback of the conventional blade locking devices is that they generally require access to both sides of the blade slot for insertion and removal. In some instances other design requirements make it impractical or inconvenient to provide such access during routine mainteance or the like, where it would be desired to remove one or more blades.

In a broad sense, these various problems have been recognized in the past, and, generally speaking, there have ice been proposals which purport to solve such problems. However, such proposals have been either complicated, expensive, or not fully adaptable for all operating conditions, as for example, where it is desire-d that the blade slots be angled relative to the axis of the rotor.

The object of the invention is therefore to providevan improved lock for a blade mounted on a rotor and in doing so to overcome the several problems identified above.

To this end, a turbomachinery rotor is employed with the usual circumferential rim having slots thereacross. Blades are mounted in these slots by means of tangs at their inner ends. A clearance is provided between the slot and the lower surface of the tang. Blade locks are disposed in these clearances, each comprising a retainer having legs embracing either the opposite ends of the tang or the opposite sides of the rotor rim, and a third leg extending in an opposite direction to engage either one side of the rotor rim or one end of the tang. A spacer lies against the retainer to maintain the blade in is radially outward position and is provided with a leg which engages the other side of the rotor rim or the other end of the slot. The retainer and spacer are held in locking position by a bolt which is preferably threaded into a threaded element on the retainer. Upon disassembly of the bolt, the spacer can be removed, permitting the blade to be shifted radially inwardly to clear shroud portions thereon for removal of the blade from the slot, and, in reverse fashion, the blade may be assembled on the rotor.

The above and other related objects and features of the invention will be apparent from a reading of the following description of the disclosure found in the accompanying drawings and the novelty thereof pointed out in the appended claims.

In the drawings:

FIGURE 1 is a longitudinal section of a portion of an axial flow compressor;

FIGURE 2 is alongitudinal section, on an enlarged scale, through the tanged root of a blade seen in FIG- URE l and taken on line II-II in FIGURE 6;

FIGURE 3 is a view taken on line III-III in FIG- URE 2;

FIGURE 4 is a section taken on line IV-IV in FIG- URE 2;

FIGURE 5 is a section taken on line V-V in FIG- URE l;

FIGURE 6 is a section, on an enlarged scale, taken generally on line VI-VI in FIGURE 5;

FIGURE 7 is a section taken on line VII-VII in FIGURE 2;

FIGURE 8 is a perspective view of one of the locking elements employed herein; and

FIGURE 9 is a perspective view of another of the locking elements employed herein.

FIGURES 1 and 5 illustrate the iirst stage of an axial ow compressor of the type employed in gas turbine engines. From the engine inlet, air passes through an annular flow passageway, defined at its outer bounds by the compressor casing 10 and at its inner lbounds by platform elements 12, some of which are stationary and some of which are integral with the compressor rotor.

Air first passes through a circumferential row of inlet guide vanes 14 and then past a circumferential row of lblades 16 which are mounted on the .compressor rotor 17. The compressor rotor comprises a 4first stage disc 18, which is connected iby a web 20 to a conical torque shaft 22, which comprises a part of the compositely formed rotor structure. Downstream of the blades 16 is a row of stator blades 2S which are mounted on the compressor casing 27. The compressor casing comprises two semicylindrical shells secured to a frame member 29 which encompasses the inlet guide vanes 14.

The outer portions of the blade 16 are of an airfoil shape and, due to their length, are provided with midspan shrouds 24 (FIGURES 5 and 6) which extend from opposite sides of the airfoil into abutting relation with corresponding shroud portions 24 on adjacent blades. Such midspan shrouds are a known means for minimizing blade vibration.

The inner ends of the 'blades 16 are provided with tangs 26 which are received by corresponding slots 28, formed in a circumferential rim 30 peripherally of the disc 18. The slots 28 are formed at an angle to the axis of the rotor which is illustrated by line x in FIGURE 6. This angled relationship corresponds to the angled relationship of the airfoil portion of the blade and minimizes stress loadings resulting from centrifugal force on the |blades during rotation.

Each blade is locked by a spacer 32, a retainer 34, and a bolt 44 which are disposed between the clearance between the lower end of the tang 26 and the bottom of the slot 28. The retainer 34 has inwardly extending legs 36 at opposite ends of a bridge portion 38. The legs 36 are angled relative to the bridge 38 corresponding to the angled relationship of the slot 28. The bridge 38 thus tits snugly against the Ibottom of the slot 2S with the legs 36 embracing opposite radial faces of the rim 30. The retainer 34 also has an outwardly extending leg 40 which is angled to engage the forward end face of the tang 26. The spacer 32 Overlies the bridge 38 and has an outwardly extending leg 42 which engages the rearward end of the tang 26. A bolt 44 passes through a hole 46 in the spacer 32 and is threaded into a self-locking nut 47 captured on the forward end of the retainer 34. The described lock thus provides by means of the legs 36 a positive clamping relative to the rim 30 and by means of the legs 40, 42 a positive clamping to the opposite end faces of the tang 26, and, at the same time, functions to positively maintain the blade 16 in a radially outwardly shifted position.

When it is desired to remove a given blade 16, one l' both of the compressor casing shells and the stator blades 25 mounted thereon are removed to provide access to the rear of the rotor rim. The appropriate 'bolt 44 is removed, thus permitting removal of the spacer 32. The blade 16 may then be shifted radially inwardly, clearing its midspan shroud elements 24 of the midspan shroud elements of adjacent blades. The blade 16 can then be slid rearwardly, bringing its tang 26 clear of the slot 28 for removal of the blade.

Similarly, the blade would be mounted by iirst placing a retainer 34 in an empty slot, next inserting the blade in the slot and shifting it outwardly. The spacer 32 `would then be inserted beneath the blade as pictured in the drawings, and the -bolt 44 threaded into the nut 47 t0 secure the locking device for operation. It will be noted that both installation and removal of blades can 'be accomplished once the compressor casing is removed from the rear side of the disc without requiring removal of the platform element 12 in advance thereof, which is for other design reasons not readily accessible for removal.

It will also be noted that the spacer 32 is provided with wings 48 which block air flow through the clearance between the bottom of the slot and the lbottom of the blade tang. These wings also prevent the retainer and spacer from shifting in this clearance under the influence of the high centrifugal forces encountered during rotation of the rotor.

It will be apparent that the described locking device could rbe essentially turned upside down where access may be had to both sides of the rotor rim. Further, while the present invention has been described as a lock for compressor blades, it could also be used on other turbomachinery blades to advantage. These and other modifications of the disclosure will occur to those skilled in the art within applicants inventive concepts which are to be limited solely by the language of the following claims.

Having thus described the invention, what is claimed as novel and desired to be secured by Letters Patent of the United States is:

1. In a turbomachinery rotor comprising a circumferential rim with slots thereacross and blades having tangs received by said slots wherein there is a clearance from one end to the other of the tang between the slot and the lower surface of the tang,

a blade lock, for each blade, comprising,

a retainer having a bridge disposed in said clearance and having a pair of legs, at opposite ends thereof, extending in one radial direction and a third leg, at one end thereof, extending in an opposite radial direction,

a spacer also disposed in said clearance and having a leg extending in the same radial direction of said third leg, and

means retaining said spacer and with said legs engaging the opposite faces of said rim and opposite ends of said tang.

2. A combination as in claim 1 wherein,

said pair of legs extend radially inwardly of the retainer bridge to engage opposite faces of said rim and retainer in assembled relation said third retainer leg and said spacer leg extend radially outwardly to engage opposite ends of said tang.

3. A combination as in claim 2 wherein,

the retaining means comprise a bolt, threadably connected with said retainer with its head clamped against the end of the spacer having the leg extending therefrom,

whereby the blade lock may be assembled and removed from one side of the turbomachinery rotor.

4. A combination as in claim 3 wherein,

the bolt extends through said clearance,

a lock. nut is attached to the end of the retainer having legs extending in opposite directions,

the spacer comprises a relatively narrow body portion through which the bolt extends and laterally extending wings, conforming to the remainder of the said Iclearance not filled by the body portion of the spacer or by the retainer,

whereby air leakage through the clearance is prevented.

References Cited UNITED STATES PATENTS 2,801,074 7/1957 Brown.

2,971,744 2/ 1961 Szydlowski. 3,076,634 2/1963 Boyle et al. 3,057,598 10/1962 Boyle et al.

EVERETTE A. POWELL, IR., Primary Examiner. 

